This invention relates generally to gaskets and more particularly as reference to a ledge gasket adapted for use in a filter element.
Examples of pertinent patents are U.S. Pat. Nos. 4,128,251; 4,056,876; 3,877,910; 3,399,516; 2,871,976 and 2,732,031.
U.S. Pat. No. 4,128,251 discloses a sealing gasket for an air filter. The gasket, preferably made of plastisol, has a soft base portion that provides a seal between the gasket and the filter medium.
In U.S. Pat. No. 4,056,876, a hot-melt adhesive is used to attach a rim to a filter element. A tight seal is formed when the adhesive is cured.
U.S. Pat. No. 3,877,910 discloses an air cleaner designed to withstand the impact of an automobile collision. The cleaner has inner and outer casings. The outer casing gives upon impact, but the inner casing, formed of stronger material, resists. The retainer does not form a filter medium seal.
U.S. Pat. No. 3,399,516 discloses two molded vinyl gaskets used to form a seal between the filter element and metal retaining piece.
U.S. Pat. No. 2,871,976 discloses a filter element used in an air-cleaner intake silencer. Two end caps, preferably formed of thermoplastic material, are molded to the ends of a filter medium. These caps form an air-tight seal with the filter medium and thus act as gaskets.
U.S. Pat. No. 2,732,031 discloses a seal and gasket combination used in an air filter. A molded piece is heat-treated and then allowed to cool while in contact with the paper element. The cooled piece acts as a seal and a gasket.
The prior art gaskets and seals proved generally adequate in sealing the end of the filter element itself. However, a second gasket was needed to provide a water seal between the filter element and the housing into which the element was inserted. That gasket was often fixed to the outer surface of a metal end retainer used to secure the filter element in the housing.
Means was also needed for facilitating removal of a used filter element from the housing. Generally, a metal plate or rim was welded to the metal end retainer for that purpose. The plate or rim had no sealing function.
The need for three separate pieces, i.e., a filter element seal, an element-to-housing water seal, and a finger grip for removal, resulted in high manufacturing costs and an unreliable and unwieldy product.